This invention relates to a method and apparatus for determining the torque of a torque generator.
Equipment used to test a torque generator which permits the testing of an internal combustion engine of a motor vehicle or the brake or the transmission or any other torque generating unit (in the following called "torque motor") under various operating conditions by having the internal combustion engine (torque motor) power-connected via its shaft to the shaft of an electrical drive is disclosed in German Offenlegungsschrift No. 3,225,035. The "internal" torque M1 generated by the combustion cycle in the motor is transmitted as a torsional moment to the mounting units which connect the motor to the foundations of the test stand. The electrical drive, e.g., an induction unit supplied by a frequency converter with a variable frequency, set at a certain electrical torque M2 by a set value and a control unit, transmits this torque M2 over its mount to the foundation of the test stand, also. The electrical drive is now in a position to simulate the load moments affecting the internal combustion engine by means of changes in its electrical torque which arise during the varying operating conditions of the vehicle. In evaluating the operating behavior of the internal combustion engine, it is not the torque itself which is generated by the electrical drive which is of interest; rather, it is the external torque ("interchange torque" MA) interchanged between the machine and the simulating drive using the shaft which is of interest.
The interchange torque can be determined by a measuring shaft installed between the induction machine and the engine. T1 defines the machine's moment of inertia and T2 the moment of inertia of the electrical drive.
For exact simulation of operating conditions one needs to know the internal torque M1 of the combustion engine which is identical with the electrical torque of the drive or the load torque of the vehicle as simulated by the drive only if the moment of inertia T1 of the machine is negligible in comparison to the load torque T2. In the other extreme case, in which T2 lcan be neglected, i.e., the drive shaft of the unit can virtually be moved with complete freedom, the internal torque M1 has been practically completely converted into the spin of the machine moment of inertia T1. In the general case, however, the relation is more complex, especially when the coupling between the induction machine and the engine is not completely rigid, but is capable, within limits, of some torsional motion. Accordingly, it will be appreciated that it would be highly desirable to provide a formula which takes the torsional motion into account.
It is an object of the present invention to provide a method and apparatus for determining the torque of a torque motor coupled to an electrical drive with a preset electrical torque.
An object of the invention is to provide a method and apparatus for measuring the torque motor torque which is interchanged with the electrical drive.
Another object of the invention is to provide a formula for determining interchange torque wich takes torsional motion into account.